The long-term objective of this research is to combine space-time signal processing and ultra-wideband radar techniques to develop imaging algorithms that will aid in the detection and treatment of early-stage breast cancer. Imaging algorithms will incorporate a space-time beamformer for focusing microwave energy at a specific location while minimizing energy elsewhere in the breast with multiple transmitting antennas. Images of backscattered energy will be obtained by processing the backscattered signals from each transmit scan location with a receive beamformer designed for the corresponding location. The class of penalized least-squares techniques will be used to design the beamformers. Performance of the algorithms will be evaluated using a realistic numerical breast model, a physical breast phantom, and breast tissue from breast reduction surgeries. The imaging capability based on the beamformers will give evidence as to the potential of implementing hyperthermia treatment. The imaging algorithms will minimize the complications, discomfort, and need for invasive procedures for women with breast cancer. [unreadable] [unreadable]